Crowds of people try to look at a notice formally announcing the birth of a son to Britain's Prince William and Catherine, Duchess of Cambridge, placed in the forecourt of Buckingham Palace, in central London, Monday afternoon, July 22.

In a statement issued four hours after the birth, Kensington Palace said: “Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 4:24pm. The Duke of Cambridge was present for the birth.

“The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news. Her Royal Highness and her child are both doing well and will remain in hospital overnight.”

The palace said the prince’s name will be announced in "due course."

The birth was also announced on a golden easel placed in the forecourt of Buckingham Palace where crowds had gathered all day.

The world’s media have been camped outside St. Mary’s Hospital in west London for the better part of two weeks waiting for the arrival of the expectant mother and then a glimpse of her offspring, who is now third in line to the British throne behind Prince Charles and Prince William.

In a brief statement Prince Charles said: “Both my wife and I are overjoyed at the arrival of my first grandchild. It is an incredibly special moment for William and Catherine and we are so thrilled for them on the birth of their baby boy.

“Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future.”

Prime Minister David Cameron also offered his congratulations, writing on Twitter: “I'm delighted for the Duke and Duchess now their son has been born. The whole country will celebrate. They'll make wonderful parents.”

It is unclear how long Kate will stay in the private Lindo Wing at St. Mary’s – the same place where Princess Diana gave birth to both William and Harry.

The baby was expected on Saturday, July 13, but like many pregnant mothers know, babies rarely decide to make an appearance on the prescribed date. Instead Prince William played in a charity polo match that day at Cirencester Park Polo Club, almost 100 miles west of the capital.

Monday, the Duke and Duchess of Cambridge arrived at the hospital around 6 a.m. without a police escort and entered via a side entrance, avoiding the front door and the banks of press and television cameras. Local press reported that Kate went into labor naturally at Kensington Palace, where the couple had spent the weekend. The delivery came on the hottest day of the year so far in London, with temperatures in the mid 90s Fahrenheit.

William had taken annual leave to be with his wife last week, and is now on two weeks' paternity leave from his job as a Royal Air Force search-and-rescue helicopter pilot.

The couple's first child will now be known officially as the Prince of Cambridge – the first royal to use that title in 100 years. The prince will be the 43rd sovereign since William the Conqueror (if he follows reigns by first Charles, then William – as is expected).

Had the baby been a girl, the new princess would have been the first royal heir to benefit from the Succession of the Crown Act of 2013, which states that whatever sex baby the royal couple had, he or she would become next in line to the throne. Previously, male heirs born later would automatically leapfrog their older sister to become king.